Assembly of Two Metal-Organic Frameworks Based on Distinct Cobalt Dimeric Building Blocks Induced by Ligand Modification: Gas Adsorption and Magnetic Properties.

Solvothermal reaction of 3,5-di(pyridin-4-yl) benzoic acid (HDPB) with Co(II) leads to a novel metal-organic framework, [Co2 O(DPB)2 (DMF)2 ]· xS (1), which represents a rare reo-type net with trigonal prismatic cobalt dimer, [Co2 O(CO2 )2 N4 ], as building blocks to construct a 3D framework containing three different types of nanoscale M12 L12 and M24 L12 polyhedron cages. More interestingly, under the same condition, the assembly of 4-methyl-3,5-di(pyridin-4-yl) benzoic acid (HMDPB) with Co(II) facilitates the formation of a cationic framework, [Co2 (MDPB)3 (DMF)](NO3 )· xS (2), with cobalt dimer, [Co2 (CO2 )3 N4 ], as building blocks. Complex 2 represents the first example of a zeolite-like network with 48-nuclear SOD cage. The significant effect of subtle modification of ligand on the overall MOFs is discussed. Moreover, the gas adsorption studies reveal that 1 exhibits permanent porosity and selective CO2 uptake. Variable-temperature magnetic susceptibility measurements show that both 1 and 2 exhibit antiferromagnetic behavior.